Carbon dioxide emissions from fossil fuel combustion is a growing source of concern, and various technologies have been, and continue to be developed, for capturing CO2 from flue gas and other gas streams. Major technologies include amine wash, physical adsorption technologies, cryogenic technologies (CO2 liquefaction). These technologies involve significant additional investment and operating costs for industrial plants. In the case of coal power plants for example, a resulting increase of the cost of electricity in the range of 4 to 5 US cents/kWh is expected. One of the main challenges today is to reduce cost of carbon dioxide capture from flue gas through efficiency improvement and capital reduction.
There are major drawbacks to all the existing systems. One possible alternative to traditional capture solutions is called anti-sublimation. The basic concept is to separate CO2 from a flue gas by cooling the flue gas to turn the CO2 into solid (de-sublimation or cryo-condensation of CO2). Indeed, at such low CO2 partial pressure (<5.11 atmosphere), the CO2 will be directly changed from gas phase to solid phase. There are two main schemes to implement such a process. The first is de-sublimation at atmospheric or very low pressure. For this scheme, a significant external refrigeration loop is required to perform such a cooling. This is known as indirect de-sublimation. The second is de-sublimation at higher pressure by expansion with solid formation. This is known as direct de-sublimation.
However, in any case, the efficiency of the process is strongly related to the ability to integrate the heat exchange. This is to say that without heat exchangers to recover energy from the flue gas notably, the efficiency of the process would be drastically decreased. Hence, there is a need in the industry for an optimized heat exchange in a carbon dioxide de-sublimation process.